1. Field of the Invention
The field of art to which this invention pertains includes rolling element bearings and more specifically four point contact bearings of the type used in low speed oscillating and turntable-type applications.
2. Description of the Prior Art
As is known from the prior art, in a four point contact or type X bearing, the groove in each of the one-piece or integral inner and outer races has two radii whose centers are offset from the plane of the ball centers, thus making possible four contact points between a ball and the raceways. The deep grooves in the bearing races combined with the four point contact geometry enables this type of bearing to resist any combination of radial, thrust and moment loading. One supplier of bearings of this type is the Kaydon Bearing Division of the Keene Corporation of Muskegon, Michigan.
Four point contact bearings are normally supplied with diametral clearance; however, this bearing is not dependent upon this clearance for its nominal contact angle and thrust capacity. On the contrary, where thrust or moment loading is considerable, the clearance should be minimized in order to prevent the angle of contact from becoming excessive. Furthermore, for many applications requiring greater stiffness, four point contact bearings are furnished by the manufacturer with an internal preload which is accomplished by using balls larger in diameter than the space provided between the raceways. In this instance, the balls and raceways have some elastic deformation without the presence of an external load.
Prior art bearings of this type require precision grinding and assembly in order to meet these criteria. Thus, normally, bearing preload is the function of the precision machining of the inner and outer races.